1. Field of the Invention
The present invention relates generally to an improved method of preparing a finely-divided polyester powder. More particularly, the invention relates to a method comprising
A. dissolving a polyester resin in benzyl alcohol and PA1 B. subsequently precipitating a finely-divided polyester powder from said solution by the use of a suitable diluent solvent.
2. Description of the Prior Art
Finely-divided polyester powders have been described in the art. See, in this regard, British Pat. No. 1,201,523 issued to Imperial Chemical Industries Limited. These polyester powders are suitable for a wide variety of uses including, for example, dulling or flattening agents in coating compositions and components in cosmetic preparations. The use of these materials in coating compositions was described in British Pat. No. 1,131,303 issued to Imperial Chemical Industries Limited and their use in cosmetic preparations has been described in British Pat. Nos. 1,093,108 and 1,202,796, both of which are also issued to Imperial Chemical Industries Limited.
As is described in British Pat. No. 1,201,523 mentioned above it has previously been known that polyester powders could be prepared by dissolving a synthetic polyester in a solvent at an elevated temperature, heating for a period of time, and subsequently mixing the warm solution with a diluent to cause precipitation of the polyester in a finely-divided form. Solvents which were previously employed to dissolve the synthetic polyester resin included propylene carbonate and ethylene carbonate. As pointed out in British Pat. No. 1,201,523, the solution of polyester had to be heated for a period of time of at least 30 minutes and, to insure that the synthetic polyester would be precipitated in a finely-divided form rather than as fibers, prolonged heating was necessary. This extended heating was required to break down or hydrolyze the polymer to reduce its molecular weight.
It has now been found, in accordance with the present invention, that a finely-divided polyester powder may be prepared without the necessity of prolonged heating by employing benzyl alcohol as the solvent in a process such as that described above.